U.S. patent number 9,153,456 [Application Number 14/100,549] was granted by the patent office on 2015-10-06 for pattern forming method using block copolymers.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. The grantee listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Kentaro Matsunaga, Yumi Nakajima.
United States Patent |
9,153,456 |
Nakajima , et al. |
October 6, 2015 |
Pattern forming method using block copolymers
Abstract
According to one embodiment, first, on a process object, a
hydrophilic guide pattern including a first hole forming pattern
having a first hole diameter and a second hole forming pattern
having a second hole diameter is formed. Then, above the guide
pattern, a frame pattern having a first opening region in a forming
region of a plurality of the first hole forming patterns and a
second opening region in a forming region of a plurality of the
second hole forming patterns is formed. Then, a first solution
including a first block copolymer having a hydrophilic polymer
chain and a hydrophobic polymer chain is supplied to the first
opening region to condense the first block copolymer. The
hydrophilic polymer chain is then removed to reduce the diameter of
the first hole forming pattern to a third hole diameter that is
smaller than the first hole diameter.
Inventors: |
Nakajima; Yumi (Yokkaichi,
JP), Matsunaga; Kentaro (Yokkaichi, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Minato-ku |
N/A |
JP |
|
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Assignee: |
Kabushiki Kaisha Toshiba
(Minato-ku, JP)
|
Family
ID: |
52111267 |
Appl.
No.: |
14/100,549 |
Filed: |
December 9, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140377956 A1 |
Dec 25, 2014 |
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Foreign Application Priority Data
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Jun 19, 2013 [JP] |
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2013-128902 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/0337 (20130101); H01L 21/0271 (20130101); H01L
21/3086 (20130101); H01L 21/3085 (20130101) |
Current International
Class: |
H01L
21/311 (20060101); H01L 21/308 (20060101); C03C
15/00 (20060101); C03C 25/68 (20060101); C23F
1/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2010-115832 |
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May 2010 |
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JP |
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2010-522643 |
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Jul 2010 |
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JP |
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2011-35233 |
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Feb 2011 |
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JP |
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2012-4434 |
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Jan 2012 |
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JP |
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2012-33534 |
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Feb 2012 |
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JP |
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2012-59802 |
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Mar 2012 |
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JP |
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2012-64783 |
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Mar 2012 |
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JP |
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2012-108369 |
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Jun 2012 |
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JP |
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WO 2008/097736 |
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Aug 2008 |
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WO |
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Other References
Naoko Kihara, "Directed Self-Assembly Lithography Technology",
Toshiba Review, vol. 67, No. 4, 2012, 6 pages (with partial English
translation). cited by applicant .
Joy Y. Cheng, et al., "Simple and Versatile Methods to Integrate
Directed Self-Assembly with Optical Lithography Using a
Polarity-Switched Photoresist", ACS Nano, vol. 4, No. 8, 2010, 9
pages. cited by applicant.
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Primary Examiner: Jung; Michael
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
What is claimed is:
1. A pattern forming method comprising: forming, above a process
object, a hydrophilic guide pattern including first hole patterns
having a first hole diameter and second hole patterns having a
second hole diameter that is larger than the first hole diameter;
forming, on the guide pattern, a frame pattern having a first
opening pattern and a second opening pattern, the first opening
pattern being disposed on the guide pattern surrounding a forming
region of a plurality of the first hole patterns that are disposed
neighboring to each other, and the second opening pattern being
disposed on the guide pattern surrounding a forming region of a
plurality of the second hole patterns that are disposed neighboring
to each other; supplying a first solution including a first block
copolymer having a hydrophilic polymer chain and a hydrophobic
polymer chain to the first opening pattern; supplying a second
solution to the second opening pattern; condensing the first block
copolymer so that the hydrophobic polymer chain comes into contact
with the guide pattern and the hydrophilic polymer chain condenses
around a center of each of the first hole patterns in the first
solution; removing the hydrophilic polymer chain condensed around
the center of each of the first hole pattern to reduce the diameter
of each of the first hole patterns to a third hole diameter that is
smaller than the first hole diameter; and processing the process
object by an etching using the guide pattern as a mask to which the
hydrophobic polymer chain is attached, wherein in the forming of
the frame pattern, the first opening pattern and the second opening
pattern are formed in a same process.
2. The pattern forming method according to claim 1, wherein in the
forming the frame pattern, a connection pattern connecting a
plurality of the first opening patterns to each other that are
positioned apart from each other or a plurality of the second
opening patterns to each other that are positioned apart from each
other is formed in the frame pattern.
3. The pattern forming method according to claim 1 wherein the
second solution includes a second block copolymer having the
hydrophilic polymer chain and the hydrophobic polymer chain; and
the method further comprising: condensing the second block
copolymer so that the hydrophobic polymer chain comes into contact
with the guide pattern and the hydrophilic polymer chain condenses
around a center of each of the second hole patterns in the second
solution with condensing the first block copolymer; and in the
removing the hydrophilic polymer chain, the hydrophilic polymer
chain condensed around the center of each of the second hole
patterns is removed to reduce the diameter of each of the second
hole patterns to a fourth hole diameter that is smaller than the
second hole diameter.
4. The pattern forming method according to claim 3, wherein
molecular weights or composition ratios of the hydrophilic polymer
chain and the hydrophobic polymer chain are different between the
first block copolymer and the second block copolymer.
5. The pattern forming method according to claim 4, wherein the
first block copolymer and the second block copolymer are copolymers
of polymethylmethacrylate and polystyrene.
6. The pattern forming method according to claim 1 wherein the
second solution includes hydrophilic polymer; and the method
further comprising: solidifying the hydrophilic polymer within each
of the second hole patterns in the second solution with condensing
the first block copolymer; and in the removing the hydrophilic
polymer chain, the hydrophilic polymer solidified within each of
the second hole patterns is removed.
7. The pattern forming method according to claim 6, wherein the
first block copolymer is a copolymer of polymethylmethacrylate and
polystyrene, and the hydrophobic polymer is
polymethylmethacrylate.
8. The pattern forming method according to claim 1, wherein the
guide pattern is a hydrophilic resist or a crosslink organic
film.
9. The pattern forming method according to claim 1, wherein, a
composition of the hydrophobic polymer chain and the hydrophilic
polymer chain in the first block copolymer or a molecular weight of
the first block copolymer is determined so that a gap between the
first hole diameter and the third hole diameter is filled with the
condensed hydrophobic polymer chain.
10. The pattern forming method according to claim 1, wherein the
guide pattern is formed by a photolithography.
11. The pattern forming method according to claim 1, wherein the
guide pattern is a pattern in which a first trench pattern
extending in a first direction and having a first width is arranged
in a second direction intersecting the first direction with the
first width, the first opening pattern is a second trench pattern
extending in the second direction and having a second width, the
second opening pattern is a third trench pattern extending in the
second direction and having a third width that is wider than the
second width, and each of the first hole patterns formed in the
guide pattern is formed at an intersection position of the first
trench pattern and the second trench pattern, and each of the
second hole patterns is formed in an intersection position of the
first trench pattern and the third trench pattern.
12. The pattern forming method according to claim 11, wherein the
first width is substantially the same as the second width.
13. The pattern forming method according to claim 11 wherein the
second solution includes a second block copolymer having the
hydrophilic polymer chain and the hydrophobic polymer chain; and
the method further comprising: condensing the second block
copolymer so that the hydrophobic polymer chain comes into contact
with the guide pattern and the hydrophilic polymer chain condenses
around a center of each of the second hole patterns in the second
solution with condensing the first block copolymer; and in the
removing the hydrophilic polymer chain, the hydrophilic polymer
chain condensed around the center of each of the second hole
patterns is removed to reduce the diameter of each of the second
hole patterns to a fourth hole diameter that is smaller than the
second hole diameter.
14. The pattern forming method according to claim 11, wherein in
the forming the frame pattern, a first connection pattern
connecting a plurality of the first trench patterns to each other
that are positioned apart from each other and a second connection
pattern connecting a plurality of the second trench patterns to
each other that are positioned apart from each other are further
formed in the frame pattern; in the supplying the first solution,
the first solution is supplied to the first connection pattern; and
in the supplying the second solution, the second solution is
supplied to the second connection pattern.
15. The pattern forming method according to claim 14, wherein
molecular weights or composition ratios of the hydrophilic polymer
chain and the hydrophobic polymer chain are different between the
first block copolymer and the second block copolymer.
16. The pattern forming method according to claim 15, wherein the
first block copolymer and the second block copolymer are copolymers
of polymethylmethacrylate and polystyrene.
17. The pattern forming method according to claim 14, wherein the
first connection pattern and the second connection pattern have
sizes that are larger than discharge ports of inkjet heads adapted
to supply the first solution and the second solution.
18. The pattern forming method according to claim 11, wherein the
guide pattern is configured by a negative resist, and the frame
pattern is configured by a positive resist.
19. The pattern forming method according to claim 1, wherein each
of the first hole patterns is provided corresponding to a forming
position of a line-and-space wiring pattern formed in a memory cell
portion, and each of the second hole patterns is provided to a
forming position of a peripheral circuit portion.
20. The pattern forming method according to claim 1, wherein a hard
mask layer is disposed between the process object and the guide
pattern.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2013-128902, filed on Jun. 19,
2013; the entire contents of which are incorporated herein by
reference.
FIELD
Embodiments described herein relate generally to a pattern forming
method.
BACKGROUND
In recent years, there has been proposed a method of forming a fine
pattern in the semiconductor device by utilizing a phenomenon that
a material is phase-separated in a self-organizing manner and a
particular regular alignment pattern is formed. For example, it has
been known that a first recess with a first width is formed in a
first region, a second recess with a second width that is wider
than the first width is formed in a second region, block copolymers
that are different in number average molecular weight are supplied
to the first recess and the second recess to be phase-separated
such that multiple phases are aligned in a line manner. Then, a
particular phase is selectively removed out of those
phase-separated and the process object is etched using the
remaining phase as a mask to form two types of line-and-space
pattern having different widths in the first region and the second
region.
In supplying the block copolymers to the first recess and the
second recess, the block copolymers are supplied in the form of a
solution in which the block copolymers are dissolved in a
predetermined solvent. Therefore, the solution supplied in the
first recess and the second recess directly diffuses into the
entire first recess and second recess.
By the way, in general in semiconductor devices, contact holes (the
via holes) are connected to the line-and-space pattern wiring
formed as described above. However, there has been no proposal of
the technique for forming the contact holes that are different in
radius in accordance with multiple types of the line-and-space
patterns that are different in width.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A to 1G are cross-sectional views schematically illustrating
an example of a procedure of a pattern forming method according to
a first embodiment;
FIGS. 2A to 2G are top views schematically illustrating the example
of the procedure of the pattern forming method according to the
first embodiment;
FIGS. 3A to 3G are cross-sectional views schematically illustrating
an example of a procedure of a pattern forming method according to
a second embodiment;
FIGS. 4A to 4G are cross-sectional views schematically illustrating
an example of a procedure of a pattern forming method according to
a third embodiment;
FIGS. 5A to 5F are top views schematically illustrating an example
of a procedure of a pattern forming method according to a fourth
embodiment; and
FIGS. 6A to 6F are cross-sectional views along A-A of FIGS. 5A to
5F.
DETAILED DESCRIPTION
In general, according to one embodiment, first, on a process
object, a hydrophilic guide pattern that includes a first hole
pattern having a first hole diameter and a second hole pattern
having a second hole diameter that is larger than the first hole
diameter is formed. On the guide pattern, a frame pattern that has
a first opening pattern in a forming region of a plurality of the
first hole patterns that are disposed neighboring to each other and
a second opening pattern in a forming region of a plurality of the
second hole patterns that are disposed neighboring to each other is
then formed. Then, a first solution including a first block
copolymer having a hydrophilic polymer chain and a hydrophobic
polymer chain is supplied in the first opening pattern. The first
block copolymer is then condensed so that the hydrophobic polymer
chain comes into contact with the guide pattern in the first
solution and the hydrophilic polymer chain condenses around the
center of the first hole pattern. Then, the hydrophilic polymer
chain condensed around the center of the first hole pattern is
removed to reduce the diameter of the first hole pattern to a third
hole diameter that is smaller than the first hole diameter.
Finally, the process object is processed by an etching using the
guide pattern as a mask to which the hydrophobic polymer chain is
attached.
By referring to the attached drawings, a pattern forming method
according to the embodiments will be described below in detail. It
is noted that the present invention is not limited to these
embodiments. Further, the cross-sectional views used in the
following embodiments are schematic views, and therefore the
relationship between the thickness and the width of the layer and
the ratio of the thicknesses of respective layers may be different
from the actual implementation. Furthermore, the film thicknesses
illustrated below are mere examples and thus the film thicknesses
are not limited to them.
First Embodiment
FIGS. 1A to 1G are cross-sectional views schematically illustrating
an example of a procedure of a pattern forming method according to
a first embodiment, and FIGS. 2A to 2G are top views schematically
illustrating the example of the procedure of the pattern forming
method according to the first embodiment.
First, a hard mask layer 11 and a hard mask layer 12 are formed in
this order above a process object such as a not-shown substrate,
for example, an insulating film where contact holes are formed. An
example of the process object may be the substrate above which
memory cells such as NAND flash memory or ReRAM (Resistive Random
Access Memory), for example, or peripheral circuit elements such as
field effect transistors for driving the memory cells are formed
and the interlayer insulating film is formed thereon. As the hard
mask layers 11 and 12, a silicon oxide film or a silicon nitride
film can be used. Then, a guide film is formed on the hard mask
layer 12. As the guide film, the thermal-crosslink organic film
such as the application type carbon film can be used. This guide
film is then processed to form a guide pattern 13.
Specifically, a not-shown SOG (Spin On Glass) film and a resist
film are formed in this order on the guide film. Then, a pattern
exposure is made to the resist film by an ArF liquid immersion
exposure apparatus to form a resist pattern for forming the holes
(the contact holes). This resist pattern has a pattern of the holes
to be connected to line-and-space wirings (the word lines or the
bit lines) that are connected to the memory cell in the memory cell
portion, and a pattern of the holes to be connected to wirings that
have widths of line and space wider than those of the memory cell
portion in the peripheral circuit portion, for example. Afterward,
by using a dry etching apparatus, a pattern transfer is made on the
SOG film using the resist pattern as the mask and then a transfer
is made on the guide film using the pattern formed on the SOG film
as the mask, and the guide pattern 13 is formed (FIG. 1A, FIG.
2A).
In the region corresponding to the memory cell portion of the guide
pattern 13, a hole forming pattern 131 is formed, and in the region
corresponding to the peripheral circuit, a hole forming pattern 132
is formed. The size of the hole forming pattern 131 is smaller than
that of the hole forming pattern 132. Further, the hole forming
patterns 131 and 132 are formed larger by a predetermined size than
the hole to be finally formed. The diameter of the hole forming
pattern 131 is 60 nm, for example, and the diameter of the hole
forming pattern 132 is 200 nm, for example.
Then, a resist is applied on the hard mask layer 12 above which the
guide pattern 13 is formed, and a resist film is formed by a
baking. A pattern exposure is then made by the ArF liquid immersion
exposure apparatus to form the resist pattern for arranging a frame
pattern. This resist pattern is formed so as to define the memory
cell portion and the peripheral circuit portion. After the
exposure, the baking is made and the development process is made,
and therefore a frame pattern 14 is formed on the guide pattern 13
(FIG. 1B, FIG. 2B). The frame pattern 14 has an opening region 141
provided in the region where the hole forming pattern 131 is formed
in the memory cell portion and an opening region 142 provided in
the region where the hole forming pattern 132 is formed in the
peripheral circuit portion. Further, as illustrated in FIG. 2B, the
frame pattern 14 may have a connection region 143 connecting the
opening regions 141 to each other that define the memory cell
portion and a connection region 144 connecting the opening regions
142 to each other that define the peripheral circuit portion.
Then, by the process such as an ink-jet method, a first solution 21
in which a first block copolymer is dissolved is dropped into the
opening region 141 and a second solution 31 in which a second block
copolymer is dissolved is dropped into the opening region 142
(FIGS. 1C to 1D, FIGS. 2C to 2D). At this time, the frame pattern
14 serves to accommodate the dropped first solution 21 in the
region (the opening region 141) in which the hole forming pattern
131 is formed and accommodate the dropped second solution 31 in the
region (the opening region 142) in which the hole forming pattern
132 is formed. Further, as illustrated in FIG. 2B, when a plurality
of opening regions 141 are connected by the connection region 143,
the drop of the first solution 21 into one opening region 141
causes the first solution 21 to be supplied also to other opening
regions 141 via the connection region 143. The same applies to the
second solution 31.
Here, the block copolymer has a structure in which multiple types
of polymer chains are coupled. Each polymer chain has a single type
of monomer chain structure. The first block copolymer and the
second block copolymer used in the first embodiment have a
structure in which a (hydrophilic) polymer chain of high affinity
with the guide pattern 13 and a (hydrophobic) polymer chain of low
affinity with the guide pattern 13 are coupled. As the first block
copolymer and the second block copolymer,
polystyrene-polymethylmethacrylate (hereafter, referred to as
Ps-b-PMMA) different in molecular weight can be used. For the first
block copolymer and the second block copolymer, the molecular
weights and the compositions of the block copolymers to be used are
determined based on the diameters (the sizes of the holes) of the
hole forming patterns 131 and 132 formed in the guide pattern 13
and the diameters of the holes (the sizes of the holes) to be
finally formed in the process object. For example, the Ps-b-PMMA of
the molecular weight of 18,000 can be used for the first block
copolymer and the Ps-b-PMMA of the molecular weight of 50,000 can
be used for the second block copolymer. In this case, the first
block copolymer and the second block copolymer are different in
composition ratio of the polystyrene (Ps) and the
polymethylmethacrylate (PMMA).
The process object is then baked, for example, at 240 degrees
centigrade for 60 seconds by a hotplate in a nitrogen atmosphere.
This causes the same type of polymer chains in the block copolymer
in the solution to be condensed to form a block (phase) made of the
same type of polymer chains. In this example, the guide pattern 13
functions as a physical guide, so that hydrophobic polymer chains
211 and 311 are condensed in the guide pattern 13 side. That is,
the hydrophobic polymer chains (Ps) 211 and 311 are condensed in
the side wall side of the hole forming patterns 131 and 132 of the
guide pattern 13 and hydrophilic polymer chains (PMMA) 212 and 312
are condensed around the center of the hole forming patterns 131
and 132, resulting in self-alignment (FIG. 1E, FIG. 2E).
Subsequently, out of the condensed polymer chains, the hydrophilic
polymer chains 212 and 312 condensed around the center of the hole
forming patterns 131 and 132 are selectively removed (FIG. 1F, FIG.
2F). For example, some parts of the hydrophilic polymer chains
(PMMA) 212 and 312 are decomposed by the irradiation of the light
of 172 nm to the substrate using an Xe.sub.2 excimer lamp.
Subsequently, an organic solvent such as developing solution or
alcohol is discharged to the substrate to form a liquid filling
state on the process object. The organic solvent is then drained
and removed and thus the decomposed object of the hydrophilic
polymer chain (PMMA) is removed. This causes the hydrophobic
polymer chain to attach to the side walls of the hole forming
patterns 131 and 132 formed in the guide pattern 13 and the hole
forming patterns 131a and 132a whose diameters have been reduced
are formed. When the above-described materials are used for the
first block copolymer and the second block copolymer, the diameter
of the hole forming pattern 131a in the memory cell portion is 20
nm and the diameter of the hole forming pattern 132a in the
peripheral circuit portion is 190 nm.
Then, the hard mask layer 12 is etched by, for example, a dry
etching using the guide pattern 13 covered with the hydrophobic
polymer chains 211 and 311 as a mask. Thereby, a hole forming
pattern 121 is formed in the memory cell portion of the hard mask
layer 12, and a hole forming pattern 122 is formed in the
peripheral circuit portion (FIG. 1G, FIG. 2G).
Furthermore, although not depicted, the hard mask layer 11 is
patterned by, for example, a dry etching using the hard mask layer
12 as a mask in which the hole forming patterns 121 and 122 are
formed. The not-shown process object is etched by, for example, a
dry etching using the patterned hard mask layer 11 as a mask. For
example, the hole (the via hole) reaching the wiring is formed by
an etching in the insulating film formed on the line-and-space
pattern wiring. As set forth, the pattern forming process is
completed.
In the first embodiment, the plural types of the hole forming
patterns 131 and 132 having the different diameters are formed in
the guide pattern 13, the frame pattern 14 that defines the hole
forming patterns 131 and 132 for each type is formed on the guide
pattern 13, the solution in which the block copolymers of the
different molecular weight or composition is supplied to each
region within the frame pattern 14, and the block copolymer is
condensed to reduce the diameters of the hole forming patterns 131a
and 132a formed in the guide pattern 13. This allows the desired
size of the holes or the via holes to be formed in the process
object all at once by using the guide pattern 13.
That is, the frame pattern 14 is provided so as to define the
regions such as the memory cell portion, the peripheral circuit
portion, and the like in which the diameters of the hole patterns
are intended to be different, so that respective regions can be
supplied with the different types of the block copolymers.
Therefore, it is no longer necessary to pattern the holes for
respective regions, so that the holes can be patterned all at once.
As a result, the number of processes can be reduced compared to the
case where respective regions are patterned, resulting in the
advantage of the reduction in the manufacturing cost of the
semiconductor device.
Further, it allows for the advantage of being able to form the hole
having a smaller diameter than the hole diameter which can be
formed by the photolithography.
Second Embodiment
FIGS. 3A to 3G are cross-sectional views schematically illustrating
an example of a procedure of a pattern forming method according to
a second embodiment.
First, a hard mask layer 11 and a hard mask layer 12 are formed in
this order above the process object such as a not-shown substrate,
for example, an insulating film where the contact holes are formed.
As the hard mask layers 11 and 12, a silicon oxide film or a
silicon nitride film can be used. On the hard mask layer 12, a
not-shown anti-reflection film is applied, and a resist film is
formed thereon. A pattern exposure is then made to the resist film
by the ArF liquid immersion exposure apparatus to form a guide
pattern 13 (FIG. 3A).
In the region corresponding to the memory cell portion of the guide
pattern 13 a hole forming pattern 131 is formed, and in the region
corresponding to the peripheral circuit a hole forming pattern 132
is formed. The size of the hole forming pattern 131 is smaller than
that of the hole forming pattern 132. Further, the hole forming
pattern 131 is formed larger by a predetermined size than the hole
to be finally formed. The diameter of the hole forming pattern 131
is 60 nm, for example, and the diameter of the hole forming pattern
132 is 200 nm, for example.
Then, a resist is applied on the hard mask layer 12 on which the
guide pattern 13 is formed, and a resist film is formed by a
baking. A pattern exposure is then made by the ArF liquid immersion
exposure apparatus to form the resist pattern for arranging a frame
pattern. This resist pattern is formed so as to define the memory
cell portion and the peripheral circuit portion. After the
exposure, a baking is made and a development process is made, and
therefore a frame pattern 14 is formed on the guide pattern 13
(FIG. 3B). The frame pattern 14 has an opening region 141 provided
in the region in the memory cell portion where the hole forming
pattern 131 is formed and an opening region 142 provided in the
region in the peripheral circuit portion where the hole forming
pattern 132 is formed. Further, similarly to FIG. 2B of the first
embodiment, the frame pattern 14 may have a connection region 143
connecting the opening regions 141 to each other that define the
memory cell portion and a connection region 144 connecting the
opening regions 142 to each other that define the peripheral
circuit portion.
Then, by the process such as an ink-jet method, a first solution 21
in which a first block copolymer is dissolved is dropped into the
opening region 141 and a second solution 32 in which a PMMA resin
is dissolved is dropped into the opening region 142 (FIGS. 3C to
3D). At this time, the frame pattern 14 serves to accommodate the
dropped first solution 21 in the region (the opening region 141) in
which the hole forming pattern 131 is formed and accommodate the
dropped second solution 32 in the region (the opening region 142)
in which the hole forming pattern 132 is formed. Further, as
illustrated in FIG. 2B, when a plurality of opening regions 141 are
connected by the connection region 143, the drop of the first
solution 21 into one opening region 141 causes the first solution
21 to be supplied also to other opening regions 141 via the
connection region 143. The same applies to the second solution
32.
The first block copolymer has a structure in which a (hydrophilic)
polymer chain of high affinity with the guide pattern 13 and a
(hydrophobic) polymer chain of low affinity with the guide pattern
13 are coupled. For the first block copolymer, the molecular weight
and the composition of the block copolymer to be used are
determined based on the diameter (the size of the hole) of the hole
forming pattern 131 formed in the guide pattern 13 and the diameter
of the hole (the size of the hole) to be finally formed in the
process object. For example, the Ps-b-PMMA of the molecular weight
of 18,000 can be used for the first block copolymer.
The process object is then baked, for example, at 240 degrees
centigrade for 60 seconds by a hotplate in a nitrogen atmosphere.
This causes the same type of polymer chains in the block copolymer
in the solution to be condensed to form a block (phase) made of the
same type of polymer chains. In this example, the guide pattern 13
functions as a physical guide, so that a hydrophobic polymer chain
211 is condensed in the guide pattern 13 side. That is, the
hydrophobic polymer chain (Ps) 211 is condensed in the side wall
side of the hole forming pattern 131 of the guide pattern 13 and a
hydrophilic polymer chain (PMMA) 212 is condensed around the center
of the hole forming pattern 131, resulting in self-alignment (FIG.
3E). It is noted that, in the hole forming pattern 132, since the
block copolymer is not dissolved in the second solution 32, there
is no self-alignment. In this example, the PMMA resin is
solidified.
Subsequently, out of the condensed polymer chains, the hydrophilic
polymer chain 212 condensed around the center of the hole forming
pattern 131 is selectively removed and the solidified PMMA resin in
the hole forming patterns 132 is removed (FIG. 3F). For example,
the hydrophilic polymer chain (PMMA) 212 and the solidified PMMA
resin are decomposed by the irradiation of the light of 172 nm to
the substrate using an Xe.sub.2 excimer lamp. Subsequently, an
organic solvent such as developing solution or alcohol is
discharged to the substrate to form a liquid filling state on the
process object. The organic solvent is then drained and removed and
thus the decomposed objects of the hydrophilic polymer chain (PMMA)
and the PMMA resin are removed. This results in a hole forming
pattern 131a that has been reduced in diameter from the hole
forming pattern 131 formed in the guide pattern 13. It is noted
that, since the hydrophobic polymer chain does not attach to the
hole forming pattern 132, there is no change in the diameter. When
the above-described material is used for the first block copolymer,
the diameter of the hole forming pattern 131a in the memory cell
portion is 20 nm and the diameter of the hole forming pattern 132
in the peripheral circuit portion is 200 nm.
Then, the hard mask layer 12 is etched by, for example, a dry
etching using the guide pattern 13 covered with the hydrophobic
polymer chain 211 as a mask. Thereby, a hole forming pattern 121 is
formed in the memory cell portion of the hard mask layer 12, and a
hole forming pattern 122 is formed in the peripheral circuit
portion (FIG. 3G).
Furthermore, although not depicted, the hard mask layer 11 is
patterned by, for example, a dry etching using the hard mask layer
12 as a mask in which the hole forming patterns 121 and 122 are
formed. The process object is etched by a dry etching using the
patterned hard mask layer 11 as a mask. For example, the hole (the
via hole) reaching the wiring is formed by an etching in the
insulating film formed on the line-and-space pattern wiring. As set
forth, the pattern forming process is completed.
In the second embodiment, the solution in which the block copolymer
is dissolved is dropped into the hole forming pattern 131 of the
guide pattern 13, and the solution in which the hydrophilic polymer
is dissolved is dropped into the hole forming pattern 132. In
addition to the advantages of the first embodiment, this allows for
the advantage that the hole diameter of the targeted region only
can be reduced.
Third Embodiment
In the second embodiment, the case has been described where the
second solution 32 having the PMMA resin dissolved therein is
supplied to the hole forming pattern 132. After the solidification
of the second solution 32, however, the PMMA resin in the hole
forming pattern 132 is removed. Thus, in a third embodiment,
described will be the case where the second solution 32 is not
supplied into the hole forming pattern 132.
FIGS. 4A to 4G are cross-sectional views schematically illustrating
an example of a procedure of a pattern forming method according to
the third embodiment. Similarly to the cases of the first and the
second embodiments, hard mask layers 11 and 12 are formed in this
order on a not-shown process object and then a guide pattern 13 is
formed that has a hole forming pattern 131 in the region
corresponding to the memory cell portion on the hard mask layer 12
and has a hole forming pattern 132 in the region corresponding to
the peripheral circuit portion (FIG. 4A). Furthermore, on the guide
pattern 13, a frame pattern 14 is formed that has an opening region
141 provided in the forming region of the hole forming pattern 131
in the memory cell portion and an opening region 142 provided in
the forming region of the hole forming pattern 132 in the
peripheral circuit portion (FIG. 4B).
Then, by the process such as an ink-jet method, a first solution 21
in which a first block copolymer is dissolved is dropped into the
opening region 141, but nothing is dropped into the opening region
142 (FIGS. 4C to 4D). At this time, the frame pattern 14 serves to
accommodate the dropped first solution 21 in the region (the
opening region 141) in which the hole forming pattern 131 is
formed. Further, as illustrated in FIG. 2B, when a plurality of
opening regions 141 are connected by a connection region 143, the
drop of the first solution 21 into one opening region 141 causes
the first solution 21 to be supplied also to other opening regions
141 via the connection region 143. The first block copolymer used
here is the same as that described in the first and the second
embodiments.
The process object is then baked, for example, at 240 degrees
centigrade for 60 seconds by a hotplate in a nitrogen atmosphere.
This causes the same type of polymer chains in the block copolymer
in the solution to be condensed to form a block (phase) made of the
same type of polymer chain. In this example, the guide pattern 13
functions as a physical guide, so that a hydrophobic polymer chain
211 is condensed in the guide pattern 13 side. That is, the
hydrophobic polymer chain (Ps) 211 is condensed in the side wall
side of the hole forming pattern 131 of the guide pattern 13 and a
hydrophilic polymer chain (PMMA) 212 is condensed around the center
of the hole forming pattern 131, resulting in self-alignment (FIG.
4E).
Subsequently, out of the condensed polymer chains, the hydrophilic
polymer chain 212 condensed around the center of the hole forming
patterns 131 is selectively removed (FIG. 4F). For example, some
parts of the hydrophilic polymer chain (PMMA) 212 is decomposed by
the irradiation of the light of 172 nm to the substrate using an
Xe.sub.2 excimer lamp. Subsequently, an organic solvent such as
developing solution or alcohol is discharged to the process object
to form a liquid filling state on the process object. The organic
solvent is then drained and removed and thus the decomposed objects
of the hydrophilic polymer chain (PMMA) 212 are removed. This
results in a hole forming pattern 131a that has been reduced in
diameter from the hole forming pattern 131 formed in the guide
pattern 13. It is noted that, since no process is applied to the
hole forming pattern 132, there is no change in the state. When the
above-described material is used for the first block copolymer, the
diameter of the hole forming pattern 131a in the memory cell
portion is 20 nm and the diameter of the hole forming pattern 132
in the peripheral circuit portion is 200 nm.
Then, the hard mask layer 12 is etched by, for example, a dry
etching using the guide pattern 13 covered with the hydrophobic
polymer chain 211 as a mask. Thereby, a hole forming pattern 121 is
formed in the memory cell portion of the hard mask layer 12, and a
hole forming pattern 122 is formed in the peripheral circuit
portion (FIG. 4G). Further, the hard mask layer 12 is used to
process the hard mask layer 11 and the not-shown process object, so
that the desired holes (the via holes) can be formed in the process
object. As set forth, the pattern forming process is completed.
In the third embodiment, the solution having the block copolymer or
the hydrophilic polymer dissolved is not supplied to the region
where no change is intended in the hole diameter. This allows for
the advantage that, in addition to the advantages of the second
embodiment, the material used for forming the holes can be reduced
compared to the second embodiment.
Fourth Embodiment
FIGS. 5A to 5F are top views schematically illustrating an example
of a procedure of a pattern forming method according to a fourth
embodiment, and FIGS. 6A to 6F are cross-sectional views along A-A
of FIGS. 5A to 5F. It is noted that, in FIGS. 5A to 5F, the
left-right direction in the figure is defined as the X direction,
and the direction orthogonal to the X direction within the drawing
sheet is defined as the Y direction.
First, a process object 51 is prepared (FIG. 5A, FIG. 6A). The
process object 51 is an object to be hole-formed such as an
insulating film. Above the process object 51, a negative resist 52
is applied. Then, a line-and-space trench pattern 521 extending in
the Y direction is formed by a photolithography technique (FIG. 5B,
FIG. 6B). The width in the X direction of the trench pattern may be
larger than the size of the hole diameter to be finally formed in
the memory cell portion.
Then, on the negative resist 52 in which the trench pattern 521 is
formed, a positive resist 53 is applied. Then, by a
photolithography technique, formed are plural types of trench
patterns 531 and 533 intersecting the trench pattern 521 and
extending in the X direction, which are different in width, and
solution drop regions 532 and 534 connected to the trench patterns
531 and 533 (FIG. 5C, FIG. 6C). The trench pattern 531 may have
substantially the same width as the trench pattern 521 and be
larger than the size of the hole diameter to be finally formed in
the memory cell portion. Further, the trench pattern 533 may have a
wider width than the trench pattern 521 and be larger than the size
of the hole diameter to be finally formed in the peripheral circuit
portion.
The intersection position of the trench pattern 521 and the trench
pattern 531 is the hole forming position in the memory cell
portion, and a substantially square hole forming pattern 541 is
formed. The hole forming pattern 541 is configured by the side
walls, which are defined by the negative resist 52 extending in the
Y direction, and the side walls, which are defined by the positive
resist 53 extending in the X direction. Further, the solution drop
region 532 is provided so as to be connected to the trench pattern
531.
The intersection position of the trench pattern 521 and the trench
pattern 533 is the hole forming position in the peripheral circuit
portion, and a rectangular hole forming pattern 542 whose
longitudinal direction is the Y direction is formed. The hole
forming pattern 542 is configured by the side walls, which are
defined by the negative resist 52 extending in the Y direction, and
the side walls, which are defined by the positive resist 53
extending in the X direction. Further, the solution drop region 534
is provided so as to be connected to the trench pattern 533.
Here, the trench pattern 521 formed by the negative resist 52 and a
part of the trench patterns 531 and 533 formed at the same height
as the negative resist 52 formed by the positive resist 53
configure a guide pattern (physical guide) defining the
condensation position of the block copolymer. Further, the trench
patterns 531 and 533 and the solution drop regions 532 and 534
formed by the positive resist 53 at the region above the negative
resist 52 configure a frame pattern.
Then, by the process such as an ink-jet method, a first solution 61
in which a first block copolymer is dissolved is dropped into the
solution drop region 532, and a second solution 71 in which a
second block copolymer is dissolved is dropped into the solution
drop region 534 (FIG. 5D, FIG. 6D). The first solution 61 dropped
into the solution drop region 532 is supplied to each trench
pattern 531 by a capillary phenomenon. Similarly, the second
solution 71 dropped into the solution drop region 534 is supplied
to each trench pattern 533 by a capillary phenomenon. Here, the
solution drop regions 532 and 534 are equal to or larger than the
discharge port of the inkjet head.
Similarly to the first embodiment, the first block copolymer and
the second block copolymer have the structure in which a
(hydrophilic) polymer chain of high affinity with the negative
resist 52 and the positive resist 53 and a (hydrophobic) polymer
chain of low affinity with the negative resist 52 and the positive
resist 53 are coupled. For the first block copolymer and the second
block copolymer, the Ps-b-PMMAs that are different in molecular
weight can be used. For the first block copolymer and the second
block copolymer, the molecular weights and the compositions of the
block copolymers to be used are determined based on the diameters
(the sizes of the holes) of the hole forming patterns 541 and 542
and the diameters of the holes (the sizes of the holes) to be
finally formed in the process object 51. For example, the Ps-b-PMMA
of the molecular weight of 18,000 can be used for the first block
copolymer and the Ps-b-PMMA of the molecular weight of 50,000 can
be used for the second block copolymer.
Then, some appropriate heat treatment or process in the solvent
atmosphere is provided resulting in that the same type of polymer
chains in the block copolymer in the solution is condensed and a
block (phase) made of the same type of polymer chain is formed. In
this example, the negative resist 52 and the positive resist 53
function as a physical guide, so that hydrophobic polymer chains
611 and 711 are condensed in the negative resist 52 side and the
positive resist 53 side. That is, the hydrophobic polymer chains
611 and 711 are condensed in the side wall side of the hole forming
patterns 541 and 542 and hydrophilic polymer chains 612 and 712 are
condensed around the center of the hole forming patterns 541 and
542, resulting in self-alignment (FIG. 5E, FIG. 6E).
Subsequently, out of the condensed polymer chains, the hydrophilic
polymer chains 612 and 712 condensed around the center of the hole
forming patterns 541 and 542 are selectively removed. For example,
some parts of the hydrophilic polymer chains 612 and 712 are
decomposed by the irradiation of the light of 172 nm to the
substrate using an Xe.sub.2 excimer lamp. Subsequently, an organic
solvent such as developing solution or alcohol is discharged to the
substrate to form a liquid filling state on the process object 51.
The organic solvent is then drained and removed and thus the
decomposed objects of the hydrophilic polymer chains 612 and 712
are removed. This causes the hydrophobic polymer chains 611 and 711
attach to the side walls of the hole forming patterns 541 and 542
and the hole forming patterns whose diameters have been reduced are
formed. Further, at this time, the different block copolymers form
the hole patterns having the different size and shape.
The process object 51 is then processed by a dry etching using the
formed hole patterns as a mask material. Then, the negative resist
52, the positive resist 53, and the block copolymer are removed by
a resist stripping process such as ashing, so that hole patterns
511 and 512 formed in the process object 51 that are different in
the desired size can be obtained (FIG. 5F, FIG. 6F).
It is noted that, while the negative resist and the positive resist
are used in the above description, the negative resist and the
positive resist can be selected as long as the trench patterns 521,
531, and 533 and the solution drop regions 532 and 534 can be
formed.
In the fourth embodiment, the line-and-space trench pattern 521 is
formed on the first resist layer, the second resist layer having
plural types of the line trench patterns 531 and 533 intersecting
the trench pattern 521 and the solution drop regions 532 and 534
are formed on the first resist layer, the solutions in which the
block copolymers are dissolved are dropped into the solution drop
regions 532 and 534, and the block copolymers are condensed to form
the hole patterns 511 and 512 whose diameters are smaller than the
holes formed by the trench pattern 521 and the trench patterns 531
and 533. Therefore, plural sizes of fine holes can be formed within
the same layer.
Further, unlike the first to third embodiments, the line trench
patterns 521, 531 and 533 intersecting to each other are used to
form the hole patterns 511 and 512 at the intersection position,
instead of first forming the hole patterns 511 and 512 in the guide
pattern. In general in the photolithography, the size of the hole
pattern can be smaller than the size of the line pattern, which
allows for the advantage that the hole patterns 511 and 512 having
further smaller diameter than those in the cases of the first to
third embodiments can be formed.
In the above embodiments, although the cases where the Ps-b-PMMA is
used as the block copolymer have been exemplified, the embodiments
are not limited to them. For example, the block copolymer can be
used, such as Polystyrene-Poly(methyl methacrylate),
Polystyrene-Poly(ethylene glycol), Polystyrene-Poly(acrylic acid),
Poly(ethylene glycol)-Polylactide methyl ether,
Poly(L-lactide)-Poly(ethylene glycol) methyl ether, Poly(ethylene
glycol) methyl ether-Poly(lactide-co-glycolide), Poly(ethylene
glycol)-Poly(.epsilon.-caprolactone) methyl ether, Poly(ethylene
oxide)-Polycaprolactone, Polystyrene-Poly(ethylene glycol),
Poly(ethylene glycol) methyl ether-Poly(D,L lactide),
Polypyrrole-Poly(caprolactone). Further, when these block
copolymers are used, the molecular weight may be changed and the
composition ratio of each polymer chain may be changed, similarly
to the case where the Ps-b-PMMA is used. Furthermore, it is not
always necessary to dissolve the same type of block copolymer for
the first solution and the second solution, and thus the different
types of block copolymers may be dissolved.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the inventions. Indeed, the novel embodiments
described herein may be embodied in a variety of other forms;
furthermore, various omissions, substitutions and changes in the
form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *